title: The guanine nucleotide exchange factor, C3G regulates differentiation and survival of human neuroblastoma cells.
abstract: Neuronal differentiation involving neurite growth is dependent on environmental cues which are relayed by signalling pathways to actin cytoskeletal remodelling. C3G, the exchange factor for Rap1, functions in pathways leading to actin reorganization and filopodia formation, processes required during neurite growth. In the present study, we have analyzed the function of C3G, in regulating neuronal cell survival and plasticity. Human neuroblastoma cells, IMR-32 induced to differentiate by serum starvation or by treatment with nerve growth factor (NGF) or forskolin showed enhanced C3G protein levels. Transient over-expression of C3G stimulated neurite growth and also increased responsiveness to NGF and serum deprivation induced differentiation. C3G-induced neurite growth was dependent on both its catalytic and N-terminal regulatory domains, and on the functions of Cdc42 and Rap1. Knockdown of C3G using small hairpin RNA inhibited forskolin and NGF-induced morphological differentiation of IMR-32 cells. Forskolin-induced differentiation was dependent on catalytic activity of C3G. Forskolin and NGF treatment resulted in phosphorylation of C3G at Tyr504 predominantly in the Golgi. C3G expression induced the cell cycle inhibitor p21 and C3G knockdown enhanced cell death in response to serum starvation. These findings demonstrate a novel function for C3G in regulating survival and differentiation of human neuroblastoma cells.
authors.affiliation: Centre for Cellular and Molecular Biology, Council of Scientific & Industrial Research (CSIR), Uppal Road, Hyderabad 500007, India. vradha@ccmb.res.in
authors.forename: Vegesna
authors.initials: V
authors.lastname: Radha
authors.forename: Ajumeera
authors.initials: A
authors.lastname: Rajanna
authors.forename: Rajesh Kumar
authors.initials: RK
authors.lastname: Gupta
authors.forename: Kunal
authors.initials: K
authors.lastname: Dayma
authors.forename: Thiagarajan
authors.initials: T
authors.lastname: Raman
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D020735:Guanine Nucleotide-Releasing Factor 2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020735:Guanine Nucleotide-Releasing Factor 2; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D005576:Colforsin; D020932:Nerve Growth Factor; D020764:cdc42 GTP-Binding Protein; D020827:rap1 GTP-Binding Proteins; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one